RE: palladium drydown and developer

The increase in dmax due to a coating is usually explained by the fact that
it reduces diffuse scattering, so that less of the light that strikes the
dmax area is reflected back to your eye, but instead behaves more like it is
striking a mirror (angle of incidence = angle of reflection). The same
principle is used, though in a more exaggerated fashion, to produce the dmax
in a daguerreotype.

Gawain

-----Original Message-----
From: Loris Medici [mailto:mail@loris.medici.name]
Sent: Friday, July 21, 2006 7:48 AM
To: alt-photo-process-l@usask.ca
Subject: RE: palladium drydown and developer

Hi Clay,

My take / understanding is: when you coat the paper with some kind of
reflective medium (gelatine, gum, wax and polyurethane wood finish as I do),
the reason of the darkening and contrast increse in the shadows is caused by
the fact that the higher refractive index of the coat causes some of the
refracting light stay in the layer... Think of the mirror effect water
causes when the light hits it surface from beneath with angles lower than xx
(was it 38? - don't remember exactly - whatever you understand what I mean).
Since less light is reflected back (and kept in the coating), density
increases.

Maybe your theory with fibers is also effective in this phenomenon but I
think the actual/main reason/cause of the dmax increase is what I describe
above.

Regards,
Loris.
Received on 07/21/06-06:15:46 AM Z